I have a 2010 2.66Ghz Intel Core 2 Duo MacBook Pro running Sierra with 8 GB RAM and 128 GB SSD.
The SSD and RAM were changed in 2013.
The macbook pro was running amazingly well for its age and I was quite happy with it until yesterday. When suddenly while I was typing and on battery power, the screen went blank though the Macbook was still on (as I hear the fan humming and see the keyboard lights on).
After that I tried to force restart it using the power button. But it won't boot. I tried resetting the PRAM, NVRAM, and SMC controllers then restarted. Now it restarts but has become extremely slow.
The SSD is encrypted and as far as the SSD decryption password login screen and apple logo with loading screen after that the macbook pro behaves as expected and is very fast.
But once it goes to desktop it slows down like crazy. I am unable to even launch any programs. Once I was able to launch activity monitor and see that the CPU was running at 95% and kernel_task was taking up 400% or something.
I haven't been able to check the RAM (but I suppose the RAM should be fine if it boots up and loads the OS?)
I also tried to boot using a USB drive MacOS backup disk and that too is extremely slow and in fact even slower than the inbuilt SSD boot up that I am unable to do anything.
The computer isnt heating up very badly or anything. On switching on the power light blinks 5 times and it doesn't detect the battery (but that may be because I tried to remove the battery and put it back again and I believe I damaged the battery sensing cable or pins I guess just adjacent to where the battery cable and pins itself go on the mother board) as pressing the button to show power left on battery shows no lights now and I am stil able to run the macbook taking away the external power source only after I boot up.
What could be wrong?